Demodulation is a vibration analysis process used to account for situations where certain machine problems remain hidden in a normal vibration reading, preventing early corrective action. Usually, these situations arise when the vibration is associated with an impact or impulse event. These events have a high frequency but a short duration. Unfortunately, when taking vibration readings, these vibration events are overwhelmed by the prominent long duration of low-frequency vibrations.
In use, demodulation first removes the low-frequency components of the vibration signals using a high-pass filter. To make the impulse events more prominent and easily identifiable later, the high-pass filtered signal is envelope-detected. The envelope-detected signal is then processed as if it were an independently-detected vibration signal. One disadvantage in demodulation is that, due to the number of filter stages, its digital implementation requires intensive signal processing.
Instead of envelope-detecting the high-pass filtered vibration signal, a technique known as PeakVue (disclosed in U.S. Pat. No. 5,895,857 to Robinson et al.) exists to extract the impulse events by signal processing the peaks of a detected vibration signal. The reference to the Robinson et al. patent and any other reference to patent specifications, external documents, or sources of information in this specification has been provided for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such documents or sources of information is not to be construed as an admission that such documents or sources of information are prior art or form part of the common general knowledge in the art in any jurisdiction.
It is an object of the present invention to either provide a method and system that implements a demodulation type process, with a high signal-to-noise ratio (SNR), without intensive signal processing, or at least provide the public with a useful choice.